Steam utility island: deaerator, boiler, desuperheater

The three units that stand between raw makeup water and steam a turbine can accept, on the IAPWS steam tables. The deaerator takes 500 mol/s of 300 K makeup and 40 mol/s of LP steam and returns 540 mol/s of saturated liquid at 5 bar (425 K) for 3.23 MW. It is a direct-contact heater, so the heating steam does not leave — it condenses into the feedwater and shows up in the outlet flow. That is the point of the unit: the reason a plant heats feedwater by injecting steam into it rather than through a tube bundle is that boiling the water is what strips the dissolved oxygen out of it. The boiler then absorbs 26.6 MW into the water and fires 31.3 MW to do it — the gap is the stack loss, and it is the number a fuel bill is written against, not the absorbed duty. The desuperheater takes that 720 K steam down to a 660 K target by spraying 25.96 mol/s of water into it. The spray rate is SOLVED, not specified: you state the temperature you want and the unit finds the water that achieves it, which is how an attemperator is actually specified. Note the outlet is 566 mol/s, more than entered it, the spray water becomes steam. Bounded: the deaerator is an equilibrium model, so it reports no rate-based O2/CO2 stripping (there is no residual-oxygen ppb number here, which is what a real deaerator is guaranteed on), and the desuperheater assumes the spray fully evaporates.